Fixes #12639 - Make sure name expansions throws a validation error on decrementing ranges

[kkthxbye-code]

Fixes: #12639

The code is a tiny bit messy, but I did my best.

Changes:

• parse_alphanumeric_range now throws a ValidationError when its passed decrementing ranges.
• The ComponentCreateForm clean method has been slightly reworked to bail out if the name field is not in cleaned_data. Not quite sure what is going on, but I think it's because validation continues even if the above ValidationError is thrown.
• The tests has been changed to expect an Exception instead of an empty list on decrementing ranges.

Tests passes now, but please give it a test to make sure I didn't mess anything up. The logic for expandable fields is a little hard to grok.